fastmodel: print stdout when build command fail
fastmodel: print stdout when build command fail

Originally we only print command stdout in verbose build. This leads
to misleading debug message when there is error happen in a non-verbose
build. This CL prints stdout when the step fails.

Change-Id: I8c34ac5576269177ae70fc5e01650193fd252b0b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40475
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Gabe Black <d3e8afea784ab4a50a2dbf9149d2eaa8478e1cbc@gmail.com>
Maintainer: Earl Ou <82591a79653dd29c9ce06ea2b578447596bef9ab@google.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5